Vascular plant species richness patterns in urban environments: Case studies from Hannover, Germany and Haifa, Israel

The continuous expansion and growth of urban and settled areas result in a mosaic of open spaces which provide important habitat for species. Species richness within the urban matrix has been commonly studied in relation to urban-rural gradients, where the richness in open-space patches has been evaluated with respect to their location along this gradient. In this study we propose that additional factors may drive richness properties, namely patch size. We established a comparative study, where species richness patterns were compared between Haifa and Hannover, with respect to two driving factors: open-area patch size and its distance from the urban edge. These relationships were assessed for the overall number of vascular plant species and for native species only. Patches were identified by classifying aerial photographs of the cities, and surveying 32 patches in Hannover and 37 patches in Haifa which were randomly selected from the delineated patches. Results indicate that in both cities distance from the urban edge was not a significant factor explaining either the total vascular plant richness in the patches, or the native species richness. In contrast, both classes of species richness were significantly related with patch size. R² values for total richness were 53 % in Hannover and 45 % in Haifa. With respect to native species richness, patch size explained a higher proportion of the variance in Hannover where R² = 73 %, and a lower proportion of the variance in Haifa (R² = 33 %). These preliminary results indicate strikingly similar driving factors in two urban landscapes which are characterized by fundamentally different histories and environments.